Preview viewport animation at 60fps?
From your comment, I gather that the FPS text is red, and below the desired rate. This is perfectly normal sadly, and just means your computer can not calculate the frames fast enough to keep up. 

The displayed frame-rate is the actual number of frames calculated per second, and is displayed in red to let you know that is not the actual rate of playback. Notice that if it is going at full speed it will display the FPS text in white.

Try cutting down on Modifiers, especially the subsurf ones, as this will exponentially increase the speed.